Currently, a portable device in the market is usually powered by either an alkaline battery, a lithium-ion battery or a NiMH battery. One drawback of battery operated devices is the inability to utilize all of the energy stored in the battery due to the natural voltage decay associated with energy depletion. This particular problem is most prevalent with alkaline batteries, which tend to suffer a drop in voltage after a relatively short period of operating time even though an adequate amount of stored energy remains. Compared with alkaline batteries, Lithium-ion and nickel-metal hydride batteries tend to maintain a more stable voltage over time, which generally allows for a higher percentage of the stored energy to be utilized. Although lithium and NiMH batteries maintain a very stable voltage over time, they suffer from a sharp voltage drop at the end of life. Predicting when this drop will occur is very difficult and often requires a great deal of testing and characterization to send a warning to a user before the actual end of the battery life.
To solve the problems identified above, some companies proposed new approaches to the power supply of portable electronic devices, as a two-battery power supply system with three power phases disclosed in the publication of US2015263561A1 by Medtronic Minimed, in which one rechargeable battery can be recharged by a replaceable battery, and the two batteries provide energy for the basic functions and/or high voltage functions respectively under different power phases; another instance is a power supply system and method using two batteries for an analyte measurement device disclosed in the publication of US20140059360A1 by Lifescan Scotland Ltd, making the working life of the device twice as long as compared to the traditional device relying on a single battery as the only power supply. Both publications involve power supply with two batteries as well as assemblies and methods for detecting the remaining capacity of the batteries, however, neither involves different charging modes depending on different operating modes of the device to meet different operating requirements, nor of them discussed the layout of the battery and the assemblies to be powered in the device, so as to say, the subject of minimizing the cost and maximizing the efficiency of the assemblies by the optimal permutations under the condition of the device being partly disposable is not considered.
A supercapacitor is a high-capacity electrochemical capacitor with capacitance values much higher than other capacitors that bridge the gap between electrolytic capacitors and rechargeable batteries whose energy storage process is a physical process with advantages of high power density, short charging time, long life, good temperature characteristics, energy conservation and environmental friendliness. It can be charged to any potential within the range of the rated voltage, and can be discharged completely, at the same time, neither over charge nor over discharge puts a negative impact on its life. Energy pulses can be transmitted repeatedly by supercapacitors and the charging-discharging circle can be repeated hundreds of thousands times. If the high power density of the capacitor and the high energy storage of the battery can be combined together, a better power supply method for portable devices can be created.